Re: Using CoreData as disconnected cache (Populating CoreData programmatically)
Re: Using CoreData as disconnected cache (Populating CoreData programmatically)
- Subject: Re: Using CoreData as disconnected cache (Populating CoreData programmatically)
- From: Alexander Lamb <email@hidden>
- Date: Thu, 12 Oct 2006 17:31:42 +0200
Hello,
What you are trying to do is interesting... since I am looking into
this as well I was wondering how you were going to handle updates.
1) From client to server.
Since you first write to your local data store (as if the programme
is actually single user), it means somewhere you will need to tell
the app "push updates to the server". You can't send the complete
local database each time. Also, since it will (probably) be
asynchronous from the user data entry, how will you handle collisions
on the server. Who is correct? The last one saving?
2) From server to client.
From what I understand, the client basically says "give me a subset
of the data". How does he specify the subset? Depending on the
subset, you might pull out most of the database (be aware of deep
copying objects).
Also, even if you get your subset, you then are disconnected. How do
you notify your client that some data he copied has changed on the
server?
Finally, is your server CoreData based or is it a more traditional
database server and you will be running sql directly to get the data
and update it (are you going through an application server or
directly to the data)?
Thanks,
Alex
--
Alexander Lamb
email@hidden
On Oct 11, 2006, at 8:18 PM, Andrew Satori wrote:
You know, sometimes all it takes is a prod :-). Thanks Chris,
that's exactly what I needed. A quick test and it works like a charm.
Andy
On Oct 11, 2006, at 2:05 PM, Chris Hanson wrote:
On Oct 11, 2006, at 9:22 AM, Andrew Satori wrote:
So in order to test this, I've started with the import, and I'm
already stuck. I cannot seem to find any examples of how to add
data to a coredata model programmatically. I can find CoreData
with bindings examples everywhere, but nothing about doing this
in code, and I'm looking for some direction to look for more
information on the subject.
What documentation have you looked at? The Low-Level Core Data
Tutorial <http://developer.apple.com/documentation/Cocoa/
Conceptual/CoreDataUtilityTutorial/> and the Core Data reference
documentation should tell you what you need to know about working
with Core Data persistent stores programmatically.
Also — and I know I mention this in practically every other
message on the subject — it's important to use correct terminology
to think about the problem as it will make both finding answers to
your questions and designing your application a lot easier. I'm
specifically referring to your "add data to a coredata model"
statement. You actually insert managed objects into a managed
object context that is connected to a persistent store coordinator
with any number of persistent stores added to it, and ask the
managed object context to save the changes you've made to your
object graph.
The terminology in the preceding paragraph directly mirrors the
names of the classes you'll need to deal with and the operations
you'll need to ask them to perform. Sometimes developers familiar
with Core Data will speak in shorthand, e.g. "context" instead of
"managed object context" and "coordinator" or "store" instead of
"persistent store coordinator" or "persistent store" but by and
large if you stick to the terms used by the classes, the path to
the solution can sometimes practically chart itself.
-- Chris
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